The present invention generally relates to an electrical connection box for a motor vehicle and a method of assembling the electrical connection box. More particularly, the present invention relates to an electrical connection box in which an electric circuit including a number of fuses, relays, etc. is disposed in a concentrated manner so as to perform reasonable branch joint of wiring harnesses and an internal circuit is constituted by wires and pressing contact terminals such that not only wiring can be performed easily and positively but the electrical connection box as a whole is structurally simplified and made compact.
In a known electrical connection box of this kind in which it is possible to easily cope with design changes of an internal circuit, a portion of a bus bar obtained by blanking an electrically conductive metal plate is formed by a wire and a pressing contact terminal which is connected to the wire through pressing contact. In case a portion of the internal circuit is formed by the wire and the pressing contact terminal, the pressing contact terminal is preliminarily attached to an upper casing or a lower casing of the electrical connection box and/or an insulating plate provided between the upper and lower casings and the wire is press fitted into the pressing contact terminal so as to be connected to the pressing contact terminal through pressing contact as disclosed in Japanese Utility Model Laid-Open Publication Nos. 3-120627 and 1-166419 and Japanese Patent Laid-Open Publication No. 6-96820.
In case a circuit formed by the wires and the pressure welding terminals and a circuit formed by bus bars is employed as an internal circuit for the electrical connection box as disclosed in Japanese Utility Model Laid-Open Publication No. 1-166419, a high-current electrically conductive member is required to be provided at a power source circuit connected to a battery. Meanwhile, at a load circuit connected to the power source circuit by branch joint, a low-current electrically conductive member may be provided and design changes are made frequently. Therefore, as shown in FIG. 1, bus bars 1 are used for the power source circuit, while wires 2 and pressing contact terminals 3 are used for the load circuit such that the bus bar 1 and the wire 2 are connected to each other by a fuse 4.
In case the wires and the pressing contact terminals are used as the internal circuit for the electrical connection box, the wires are required to be laid inside the upper and lower casings. However, since the pressing contact terminals are driven into the upper and lower casings in advance, the pressing contact terminals prevents the wires from being laid in the upper and lower casings easily. Furthermore, there is also such a problem that since each of the upper and lower casings has a peripheral wall, a wiring head interferes with the peripheral wall so as to restrain wiring space. In order to solve these problems, a wiring die 5 shown in FIGS. 2A and 2B has been used. The wiring die 5 is formed with a groove 6 conforming to a wiring pattern of a wire 2 and the wire 2 is inserted into the groove 6 while being fed from a wire feeder 7 by a pair of head rollers 8. At this time, since the wire 2 has rigidity to some extent and show a strong tendency to wind, depth of the groove 6 is set so as to be twice or more as large as diameter of the wire 2 such that the wire 2 is held in the groove 6 positively without moving away from the bottom of the groove 6.
After the wire 2 has been placed in the groove 6 of the wiring die 5 as described above, the upper or lower casing or the insulating plate, to which the pressing contact terminals are preliminarily attached, is set on the wiring die 5 such that the pressing contact terminals are brought into contact with the wire 2. Subsequently, by projecting push pins from surface of the wiring die 5, the upper or lower casing or the insulating plate, to which the wire 2 and the pressing contact terminals are attached, is pushed out of the wiring die 5.
If a portion of the internal circuit of the electrical connection box is formed by the wires and the pressing contact terminals, the wiring die is required so as to lay the wires in a predetermined pattern as described above. Thus, a number of wiring dies should be prepared for different wiring patterns. Meanwhile, a transfer step in which the wires placed in the grooves of the wiring die are connected, through pressing contact, to the pressing contact terminals attached to the upper or lower casing or the insulating plate is required to be performed, thereby resulting in rise, of production cost of the electrical connection box and increase of the number of operational steps.
Meanwhile, in case the pressing contact terminals are attached to the upper or lower casing and the wires are connected to the pressing contact terminals simultaneously with laying the wires on an inner face of the upper or lower casing, such a problem arise that since an outer face of each of the upper and lower casings are made uneven by connector portions, it is impossible to lay and connect the wires to the pressing contact terminals stably. Furthermore, since pressing contact of the wires with the pressing contact terminals attached preliminarily to the upper or lower casing and assembly of the upper and lower casings are performed concurrently, it is disadvantageously impossible to check whether or not the wires are held in pressing contact with the pressing contact terminals properly.
Moreover, if the power source circuit disposed at the upstream side of the internal circuit of the electrical connection box is formed by the bus bars and the load circuit disposed at the downstream side of the internal circuit of the electrical connection box is formed by the wires and the pressing contact terminals as shown in FIG. 1, configuration of the internal circuit becomes complicated and the number of operational steps increases due to difference between structure for attaching the bus bars to the electrical connection box and structure for attaching the wires and the pressing contact terminals to the electrical connection box. In addition, since not only the wiring die but a die for forming the bus bars is required to be provided, production cost of the electrical connection box is raised greatly. Moreover, when the electrical connection box is used in common with other types of motor vehicles, such a drawback may be incurred frequently in which design changes of the power source circuit are required to be made frequently but cannot be made.
This drawback can be eliminated when the power source circuit is also formed by the wires and the pressing contact terminals. However, diameter of the wires for the power source circuit is large, while diameter of the wires for the load circuit is small or medium-sized. Therefore, if these wires having different diameters are laid on an identical plane, area required for laying the wires is increased, so that space for installing the electrical connection box increases and thus, such a case may happen that the electrical connection box cannot be installed at some locations.
Meanwhile, when the wires are laid on the upper or lower casing or the insulating plate, the wires should not overlap each other, thus resulting in such a problem that the wiring pattern is forced to be made complicated. In this case, bending of the wires is limited by the strength, etc. As the number of the wires to be laid increases, this problem becomes more conspicuous.
Generally, as shown in FIG. 3, the pressing contact terminal 3 is formed by blanking an electrically conductive metal plate having a uniform thickness and is formed, at its upper and lower portions, with a terminal portion 3c and a pressing contact portion 3b, respectively. The terminal portion 3c has a shape of an elongated tab, while the pressing contact portion 3b has a downwardly opening slot 3a. By fitting into the slot 3a the wire 2 laid in a casing C, the pressing contact portion 3b is thrust into an insulating coating 2a of the wire 2 so as to be connected to a conductor 2b of the wire 2. Through a relay terminal R having female terminals at its opposite ends, the terminal portion 3c is electrically connected to a platelike terminal T of a relay, a fuse or the like.
Since the terminal portion 3c of the known pressing contact terminal 3 acts as a male terminal having a shape of a tab, the terminal portion 3c cannot be directly connected to the terminal T having a shape of a tab, e.g., a relay, a fuse, etc., so that the relay terminal R should be used between the terminal portion 3c and the terminal T and thus, a height h of the electrical connection box in the direction of connection between the terminal portion 3c and the terminal R is required to be increased. As a result, the electrical connection box is made larger in size.
Furthermore, since the relay terminal R is required to be provided, the number of components for the electrical connection box increases and assembly of the electrical connection box is troublesome.
In order to solve the above mentioned problems of the known electrical connection box of FIG. 3, a pressing contact terminal 3' shown in FIG. 4 may be considered. The pressing contact terminal 3' has a base plate portion 3d extending from the pressing contact portion 3b and a pair of curled portions 3e are, respectively, curved laterally inwardly towards each other from opposite sides of the base plate portion 3d so as to form a pair of female terminal portions 3c'. Thus, if the male terminal T having a shape of a tab is inserted in between the curled portions 3e and the base plate portion 3d, the relay terminal R of FIG. 3 can be eliminated.
However, since the circuit connected to the terminal T of a relay, a fuse, etc. is usually a power source circuit through which high current flows, a large-diameter wire should be employed for forming the power source circuit in place of the bus bar. Therefore, the pressing contact terminal to which the large-diameter wire is connected through pressing contact should have large thickness for securing high strength and have large area of its contact with the wire. However, unless the curled portions 3e have a small thickness of, for example, 4 mm or less, it is difficult to form the curled portions 3e. Hence, in the case of the pressing contact terminal for the large-diameter wire, the female terminal portion 3c' cannot be formed by providing the curled portions 3e and thus, the relay terminal R is forced to be used.